1. Technical Field
The present invention relates to a flame-retardant ABS resin technique, and more especially, to a thermoplastic flame-retardant alloy and a method for preparing it.
2. Description of Related Art
Flame-retardant ABS resin is widely applied in the shells of the household audio-visual equipment and the office electronic equipment, and other fields such as white household appliances and power changeover devices due to its good mechanical property, processing property and post-processing property, low molding shrinkage and superior size stability. A common flame-retardant ABS formula contains ABS resin, brominated flame retardant, stibium oxide or salt, anti-dripping agent, lubricant and other necessary processing aids in order to make the product with a balance of rigidity, toughness, fluidity and flame resistance. However, the double bond in the rubber of the ABS resin and the nitrile group of the acrylonitrile are easy to cause ring reaction under the ultraviolet, which leads to yellowing of the material, thus having limits on some weather-resistant occasion or the using of outdoor part because of the bad weatherability. Besides, the glossiness and the surface hardness are worse than PC/ABS or PC. Therefore, the appearance effect and scratch resistance are inferior to the abovementioned two materials.
In order to improve the ultraviolet resistance and the impact resistance of the ABS resin, Monsanto Inc., an American company, once prepared the mix alloy (U.S. Pat. No. 5,162,416) regarding SMA as the compatibilizer and the sodium stearate as the nucleating agent. The U.S. Pat. No. 5,082,897 also discloses that ABS, PC, PCTG binary/ternary alloy has a better mechanical property and weatherability than the three resins. Meanwhile, an obvious effect can be realized by applying PCTG on the surface of the ABS resin as the weatherability coating (E.P. Pat. No. 7,273,650 B2).
The study above aims at preparing the alloy by means of the ABS resin and the polyester/co-polyester without considering the requirements for application as the modified material such as processing property and physical property. In addition, the flame resistance of the material is firstly required in order to meet the safety requirements in appliances area. However, so far there is no disclosure about the flame-retardant ABS/polyester/co-polyester alloy.
According to our research, with the introduction of the PET or the co-polyester or the mixture of PET and the co-polyester in the flame-retardant ABS system (including ABS resin, flame retardant, flame-retardant aid, anti-dripping agent and other necessary processing aids), the pencil hardness of the part surface is heightened from the original 2B to HB, the glossiness is up about 10%, the notched impact strength is increased by about 20%, and the bending and drawing strength are improved to a certain extent. After being exposed under the ultraviolet, the chromatic difference of the color plate prepared is about 30% lower than the plate without polyester/co-polyester after 100 hours, that is, the surface hardness, glossiness, mechanical property and weatherability of the material are greatly improved.